Bauer made that argument in the Citizens United case, and the court didn’t heed his warning. Instead, in the seminal 2010 ruling, it sided with the conservative advocacy group of that name and legalized unlimited corporate and union political ad spending. The ruling, which found restrictions on such spending unconstitutionally infringed upon the First Amendment, removed restrictions on anonymously funded nonprofit groups. Plus, it emboldened big donors, who got a new avenue for mega-checks when a subsequent lower court case paved the way for the creation of super PACs.

But Bauer’s most famous client had in role in this as well: In 2008, Obama opted out of the government program for the public financing of presidential campaigns, which had been set up during the Watergate era to avoid the very dollar-for-dollar arms-race mentality that defines running for president in the 21st century .

Now, when it comes to fundraising, it’s more cost effective for candidates and their allies to schmooze a few hundred rich folks than it is to cultivate a base of several hundred thousand activists through labor-intensive — and costly — online and direct-mail solicitations and phone banking.

“There is simply a better payoff by courting seven-figure donors than there was previously,” said Matt Schlapp, a former White House political director for George W. Bush, whose political operation combined aggressive outreach to small donors with cool perks for donors who collected big checks from rich friends and associates. “And that has caused finance consultants to rethink how they spend their time and how they put their projects together.”

Case in point: Obama needed just 60 people to pull in $2.4 million at a Manhattan fundraiser last month.

Small-donor fundraising yield can vary widely depending on time of year — it’s harder to raise money during the summer vacation months, for instance — and spike or fall at major events in the campaign like the Supreme Court’s “Obamacare” decision or debate stumbles.

Plus, it’s not cheap, involving major up-front investments in list maintenance, direct mail, phone banking and text messaging. Even the campaign-branded swag given to small donors adds up, with Romney’s campaign dropping about $1.4 million on promotional items and Obama’s spending at least $7.3 million on merchandise including high-fashion items produced by top designers, such as a Tory Burch tote, which sells for $75.

Even with all that, both Obama and Romney partisans tout their small donors, which they point to as evidence of their campaigns’ grass-roots support.

Romney’s campaign on Monday announced that in July donors who gave $250 or less provided more than 25 percent of the $101 million raised by the campaign, the Republican National Committee and the Romney Victory joint fund created by the campaign and the Republican National Campaign.